Photointerrupter and case thereof

ABSTRACT

A case ( 3 ) of a photointerrupter (A) includes a pair of projections ( 35 ) for preventing a light source ( 1 ) and a photodetector ( 2 ) from coming out of a respective one of paired receiving portions ( 30 ). Each of the projections ( 35 ) is connected to a respective first wall ( 32 A) defining the respective receiving portion ( 30 ) of the case on an extension line of a respective slit ( 34 ) for light transmission. Therefore, the case ( 3 ) need not be formed with a large slit other than the slit ( 34 ), so that disturbing external light is less likely to enter the receiving portions ( 30 ).

TECHNICAL FIELD

The present invention relates to a photointerrupter used or detecting adesired object or desired part of an object. It also relates to a caseused for such a photointerrupter.

BACKGROUND ART

A typical prior art photointerrupter, which is disclosed in JP-U-6-50365for example, has such a structure as shown in FIGS. 12 and 13 of theaccompanying drawings. The illustrated photointerrupter B comprises anLED lamp 7, a photodetector 8 and a case 9. The LED lamp 7 as a lightemitting element comprises an LED chip 70 sealed in a transparent resin71. The LED lamp has two leads 72. The photodetector 8 comprises a lightreceiving element sealed in a transparent resin 81. The photodetectorhas two leads 82. The case 9 includes a pair of receiving portions 90for receiving the LED lamp 7 and the photodetector 8, respectively, anda plurality of walls for defining the receiving portions.

Each of the receiving portions 90 has an opening 91 at the bottom. Theplurality of walls include a pair of opposite walls 92A each of which isformed with a slit 94 for allowing light emitted from the LED lamp 7 totravel toward the photodetector 8. When an object to be detected (notshown) exists between the slits 94, the object blocks light from the LEDlamp 7. As a result, light cannot be received by the photodetector 8 sothat signal output from the two leads 82 stops. In this way, thepresence or absence of an object is checked.

The case 9 further includes another pair of walls 92B each of which isformed with a projection 95 having an increasing thickness toward itsupper end. The upper end of each projection 95 partially extends intothe corresponding receiving portion 90. With this structure, the upperend of each projection 95 is brought into engagement with the resin 71of the LED lamp 7 or the resin 81 of the photodetector 8, thereby fixingthe LED lamp 7 or the photodetector 8 in the corresponding receivingportion 90. In the photointerrupter B, therefore, the LED lamp 7 and thephotodetector 8 need not be press-fitted into the receiving portions 90,so that deformation of the LED lamp 7 and the photodetector 8 due tosuch press fit can be avoided. Moreover, since a lid which is separatefrom the case 9 need not be provided to fix the LED lamp and thephotodetector 8, it is possible to reduce the number of parts of thephotointerrupter.

However, the above-described prior art apparatus has the followingproblems.

In the prior art apparatus, the slits 94 for light transmission areprovided in the walls 92A of the case 9, whereas the projections 95 areprovided in the walls 92B which are separate from the walls 92A.Therefore, in forming the case 9 by resin molding, large openings 99 forforming the projections 95 are provided in the walls 92B. Specifically,as shown in FIG. 14, when the case 9 is formed by using a mold 4Ccomprising an upper mold member 48 and a lower mold member 49, portions48 a of the upper mold member 48 need to be disposed above clearances95′ for forming the projections 95 in the case 9. As is clear from theconfiguration of the projections 95 shown in FIG. 12, part of the uppermold member 48 needs to extend on both sides of the correspondingclearance 95′ for forming the projection 95. Accordingly, the case iscorrespondingly formed with openings 99.

Since each of the walls 92B of the case 9 is formed with an opening 99,disturbing external light is likely to enter the corresponding receivingportion 90 at the opening 99. In the prior art apparatus, therefore,disturbing external light is received by the photodetectors 8, whichleads to malfunction of the apparatus.

DISCLOSURE OF THE INVENTION

It is an object of the present invention to provide a photointerrupterand a case for a photointerrupter which are capable of eliminating orreducing the problems of the above-described prior art apparatus.

In accordance with a first aspect of the present invention, there isprovided a photointerrupter comprising a light source, a photodetector,and a case. The case includes a pair of receiving portions each of whichis open at one end for receiving the light source or the photodetector,and a plurality of walls defining the pair of receiving portions. Theplurality of walls of the case include a pair of first walls each ofwhich is formed with a respective elongated slit. The case furtherincludes a pair of projections each of which projects into a respectiveone of the receiving portions for preventing the light source or thephotodetector from coming out of the receiving portion. Each projectionis connected to a respective one of the first walls on an extension lineof the respective slit.

Preferably, each projection may be connected to a longitudinal end edgeof the respective slit.

Preferably, the case may be made of a synthetic resin, and the pair ofprojections may be integral with the plurality of walls.

Preferably, each projection may include a base end connected to therespective first wall and a tip end projecting into the respectivereceiving portion for engagement with one of the light source and thephotodetector.

Thus, according to the present invention, in forming the case of thephotointerrupter by resin-molding using a mold, part of the mold forforming the slit can be utilized for forming the projection. Therefore,unlike the prior art apparatus, the case of the present invention is notformed with a large opening at portions other than the first walls atwhich the slits are formed. Therefore, disturbing external light is lesslikely to enter the receiving portions, which enhances reliability ofdetection by the photointerrupter.

Preferably, each projection may be elastically deformable for allowingmovement of the tip end toward the respective first wall.

With this structure, each of the light source and the photodetector canbe easily inserted into the corresponding receiving portion by pushingthe tip end of the corresponding projection by the light source or thephotodetector toward the corresponding first wall. After the lightsource and the photodetector are inserted into the respective receivingportions, the tip end of each projection projects into the correspondingreceiving portion due to the elastic recovery. Thus, fixing of the lightsource and the photodetector can also be performed easily.

Preferably, a rounded connection may be provided between the base end ofeach projection and the respective first wall.

With this structure, a gradually curving outer configuration is providedat the connection between the base end of each projection and thecorresponding first wall. Therefore, even when a force is applied to thetip end of each projection and the base end is subjected to a bendingstress, it is possible to prevent a stress concentration on a particularportion of the base end. Accordingly, even when a pulling force (a forceto pull out the light source or the photodetector from the correspondingreceiving portion through the opening) is generated and each of theprojection is pressed by the light source or the photodetector, it ispossible to prevent the projection from easily breaking. Thus, the lightsource and the photodetector can be reliably fixed.

Preferably, each of the light source and the photodetector may include abottom surface facing the opening of the respective receiving portionand a side surface facing the respective first wall, and the tip end ofeach projection may include a first surface and a second surface forengagement with the bottom surface and the side surface, respectively.

With this structure, since the second surface of each projection engagesthe side surface of the light source or the photodetector, theprojection is prevented from rotating in a direction in which the secondsurface faces toward the side surface of the light source or thephotodetector. Therefore, even when a pulling force is exerted on thelight source or the photodetector which, as a result, presses the firstsurface of the corresponding projection toward the opening of thecorresponding receiving portion, it is possible to prevent theprojection from easily rotating in that direction. Thus, fixing of thelight source and the photodetector becomes more reliable.

Preferably, each projection may be connected to the respective firstwall at a portion away from a longitudinal end edge of the respectiveslit, and the projection is wider than the slit.

With this structure, even in the case where each slit needs to benarrowed to enhance the detection ability of the photointerrupter, theprojection can be made wider than the slit to have a sufficientstrength.

Preferably, the light source may comprise a light emitting elementsealed in a resin, and a plurality of leads projecting from the resin inelectrical connection with the light emitting element.

Preferably, the photodetector may comprise a light receiving elementsealed in a resin, and a plurality of leads projecting from the resin inelectrical connection with the light receiving element.

In accordance with a second aspect of the present invention, there isprovided a case for a photointerrupter comprising a pair of receivingportions each of which is open at one end, a plurality of walls definingthe pair of receiving portions. The plurality of walls of the caseinclude a pair of first walls each of which is formed with a respectiveelongated slit. The case further includes a pair of projections each ofwhich projects into a respective one of the receiving portions forpreventing the light source or the photodetector accommodated in therespective receiving portion from coming out of the receiving portion.Each projection is connected to the respective first wall on anextension line of the respective slit.

The case of the photointerrupter having the above-described structurecan obtain the same advantages as those obtained by the photointerrupterprovided in accordance with the first aspect of the present invention.

Other features and advantages of the present invention will becomeclearer from the detailed description given below with reference to theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing an example of photointerrupter inaccordance with the present invention.

FIG. 2 is a sectional view taken along lines II—II in FIG. 1.

FIG. 3 is a bottom view of the photointerrupter shown in FIG. 1.

FIG. 4 is a sectional view showing an principal portion of a mold usedfor forming the photointerrupter.

FIG. 5 is a sectional view showing the principal portion of the mold ofFIG. 4 in an open state.

FIG. 6 is a sectional view showing a step of assembling thephotointerrupter shown in FIG. 1.

FIG. 7 is a sectional view showing another example of photointerrupterin accordance with the present invention.

FIG. 8 is a plan view showing another example of case for aphotointerrupter in accordance with the present invention.

FIG. 9 is a sectional view taken along lines IX—IX in FIG. 8.

FIG. 10 is a sectional view showing a principal portion of another moldused for forming the photointerrupter.

FIG. 11 is a cross sectional view showing another example ofphotointerrupter in accordance with the present invention.

FIG. 12 is a perspective view showing an example of prior art apparatus.

FIG. 13 is a sectional view taken along lines XIII—XIII in FIG. 12.

FIG. 14 is a sectional view showing a principal portion of a mold usedin a prior art.

BEST MODE FOR CARRYING OUT THE INVENTION

Preferred embodiments of the present invention will be described belowwith reference to the accompanying drawings.

FIGS. 1 through 3 illustrate a first embodiment of the presentinvention. The illustrated photointerrupter A is a transmission typephotointerrupter which comprises an LED lamp 1, a photodetector 2 and acase 3.

The LED lamp 1 as a light emitting element comprises an LED 10 sealed ina transparent resin 11 for example. The resin 11, which is generally inthe form of a parallelepiped, has a bottom surface 11 a, from whichproject two leads 12 electrically connected to the LED 10.

The photodetector 2 comprises a photodiode 20 for example as a lightreceiving element and a transparent resin 21 sealing the photodiode.Similarly to the resin 11, the resin 21 is generally in the form of aparallelepiped and has a bottom surface 21 a, from which project twoleads 22 electrically connected to the photodiode 20.

The case 3 may be made of e.g. black polycarbonate by molding, asdescribed later. The case 3 includes a pair of receiving portions 30 forreceiving the LED lamp 1 and the photodetector 2, respectively. Each ofthe receiving portions 30 is in the form of square-cornered recesscorresponding in shape to the resin 11 or 21 for preventing the LED lamp1 or the photodetector 2 from changing its orientation within thereceiving portion. The receiving portion 30 has a respective opening 31at the bottom thereof for inserting the LED lamp 1 or the photodetector2.

For defining the receiving portions 30, the case 3 includes a pair offirst walls 32A, a pair of second walls 32B and a plurality of otherwalls, which are integral with each other. The first walls 32A face eachother via a space 33. Each of the paired first walls 32A is formed witha slit 34. The provision of the slit 34, which extends in the heightdirection of the case 3 (vertical direction in FIGS. 1 and 2), enablesthe photodetector 2 to receive light emitted from the LED lamp 1. Thesecond walls 32B, which are the upper walls of the receiving portions30, are connected transversely to the corresponding first walls 32A.Each of the slits 34 extends into the corresponding second wall 32B.

Further, the case 3 is integrally formed with a pair of projections 35.Each of the projections 35 has a base end which is connected to alongitudinally lower edge 32A′ of the slit 34 of the corresponding firstwall 32A. The projection 35 rises obliquely from the lower edge 32A′ sothat its tip end projects deeper into the corresponding receivingportion 30 than the slit 34. However, the projection 35 can beelastically deformed for pivotal movement about its base end in adirection indicated by an arrow Na in FIG. 2. The projection 35 has awidth S1 (See FIG. 3) which is equal to or smaller than that of the eachslit 34.

The paired first walls 32A are connected together by a generallyhorizontal wall 36, and the base end of each projection 35 is connectedto the corresponding one of the first walls 32A at a portion where thefirst wall 32A is connected to the horizontal wall 36. A roundedconnection of a suitable radius R1 is provided between the base end ofthe projection 35 and the wall 36. Similarly, a rounded connection of asuitable radius R2 is provided between the base end and thecorresponding first wall 32A.

The tip end of each projection 35 is provided with a first surface 37 aoriented upward and a second surface 37 b perpendicularly connectedthereto. The first surface 37 a engages with the bottom surface 11 a ofthe resin 11 for the LED lamp 1 or the bottom surface 21 a of the resin21 for the photodetector 2. The second surface 37 b engages a sidesurface 11 b of the resin 11 or a side surface 21 b of the resin 21.Each of the side surfaces 11 b, 21 b faces the corresponding first wall32A and slit 34.

In this embodiment, the LED lamp 1 and the photodetector 2 are generallyidentical in outer configuration and size. Therefore, the case 3 is madesymmetrical, as clearly shown in FIG. 2. However, the LED lamp 1 and thephotodetector 2 may have different configurations and sizes. In such acase, the paired receiving portions 30 also have different sizes andconfigurations.

The case 3 is formed by using e.g. a mold 4 comprising an upper moldmember 40 and a lower mold member 41, as shown in FIG. 4. The upper moldmember 40 and the lower mold member 41 define a cavity for filling resinwhich later becomes portions of the case 3. The upper mold member 40includes a pair of projections 40 a each of which includes a portion 34′(solid portion) corresponding to the slit 34 of the case 3 and a portion30′ (solid portion) corresponding to a portion of the receiving portion30. The projections 40 a of the upper mold member 40 are located aboveclearances 35′ for forming the projections 35 of the case 3. Each of theprojections 40 a has surfaces 37 a′, 37 b′ for forming the first and thesecond surfaces 37 a, 37 b of the corresponding projection 35, and asurface 37 c′ for forming another upper surface of the projection 35.The surfaces of the projection 35 other than those described above areformed by a surface 41 a or other surfaces of the lower mold member 41.

The case 3 is formed by filling resin into the cavity of theabove-described mold 4 followed by hardening the resin. After molding,the case 3 is removed from the mold 4. In lifting the upper mold member40, the projections 40 a including the surfaces 37 a′˜37 c′ movelongitudinally along the slits 34 without hindrance. After the uppermold member 40 is thus lifted, the case 3 can be readily removed fromthe lower mold member 41. Thus, in the above-described case 3, each ofthe slits 34 is utilized as a slit for forming the correspondingprojection 35. Therefore, slits or openings other than the slits 34 neednot be formed in the case 3.

The photointerrupter A having the above-described structure is preparedby inserting the LED lamp 1 and the photodetector 2 into the pairedreceiving portions 30 of the case 3, as shown in FIG. 6. In insertingthe LED lamp and the photodetector, the resin 11 of the LED lamp 1 andthe resin 21 of the photodetector 2 push the respective projection 35 inan arrow Nb direction in FIG. 6, making the projection 35 retreat towardthe respective slit 34. Therefore, the projections 35 do not hinder theinsertion of these components. When the LED lamp 1 and the photodetector2 are inserted up to the upper end of the respective receiving portions30, the projections 35 return, due to the elastic recovery, to theiroriginal state, projecting into the respective receiving portions 30, asclearly shown in FIG. 2. As a result, the first surfaces 37 a of theprojections 35 engage the bottom surface 11 a of the resin 11 and thebottom surface 21 a of the resin 21, respectively. Therefore, theprojections 35 prevent the LED lamp 1 and the photodetector 2 fromlowering, thereby appropriately fixing the LED lamp 1 and thephotodetector 2 in respective receiving portions 30.

In the above-described photointerrupter A, the walls defining thereceiving portions 30 need not be formed with slits or openings otherthan the slits 34. Therefore, it is possible to eliminate or lessen thepossibility that disturbing external light enters the receiving portions30 at portions other than the slits 34. As a result, the photodetector 2can be prevented from receiving disturbing external light which maycause erroneous object detection.

When the photointerrupter A is actually used, a force F may be generatedwhich causes the LED lamp 1 and the photodetector 2 to descend relativeto the case 3 (See FIG. 2). For example, the photointerrupter A may bemounted on a desired mother board by the insertion of the leads 12, 22into respective through-holes of the mother board. In this state, whenan upward force is applied to the case 3, a force F is applied to theLED lamp 1 and the photodetector 2, as mentioned above.

In the photointerrupter A, however, the LED lamp 1 and the photodetector2 are prevented from coming out through the respective openings 31 undera force F, as described above.

First, when a force F is applied to the LED lamp 1, the first surface 37a of the tip end of the corresponding projection 35 is pressed downwardby the bottom surface 11 a of the resin 11. Therefore, the projection 35is subjected to a bending moment in an arrow Nc direction and aresulting bending stress. The stress becomes maximum at the base end ofthe projection 35, specifically at the connection between the base endand the corresponding first wall 32A. On the other hand, the connectionis upwardly and downwardly rounded with suitable radii R1, R2,respectively, so that the cross section of the connection varies onlygradually. This prevents the above-described stress from beingintensively applied on a particular portion of the connection.Therefore, bending breakage of the projection 35 due to theabove-described stress can be avoided. A stress concentration can beprevented even when the connection is rounded only upwardly or onlydownwardly. Therefore, the connection may be rounded only upwardly oronly downwardly according to the present invention.

Secondly, when a force F exerted on the LED lamp 1 tends to rotate theprojection 35 in the arrow Nc direction, the second surface 37 b of theprojection 35 strongly engages the side surface 11 b of the resin 11.Therefore, the projection 35 does not further rotate in the arrow Ncdirection. As a result, a bending stress is less likely to be exerted onthe projection 35, which prevents the projection 35 from being bent atits base end.

The same advantages can be obtained in the case where a downward forceis exerted on the photodetector 2. With the photointerrupter A,therefore, the projection 35 functions to suitably fix the LED lamp 1 orthe photodetector 2 within the corresponding receiving portion 30. Sincethe projection 35 is thus configured to prevent bending breakage, theprojection 35 need not have a large wall thickness. Therefore, it ispossible to realize thickness reduction of the case 3, which enables aproduction cost reduction and an overall size reduction of theapparatus. FIG. 7 illustrates a second embodiment of the presentinvention. In FIG. 7 and the subsequent figures, the elements which areidentical or similar to those of the first embodiment are designated bythe same reference signs as those used for the first embodiment.

In the photointerrupter Aa shown in FIG. 7, projections 35 do notinclude, at their tip ends, second surfaces 37 b which are provided inthe first embodiment. Even with such a structure, each tip end of thepaired projections 35 is brought into engagement with the bottom surface11 a of the resin 11 of the LED lamp 1 or the bottom surface 21 a of theresin 21 of the photodetector 2. As a result, it is possible to preventthe LED lamp 1 and the photodetector 2 from coming out of the respectivereceiving portions 30 downwardly. Thus, this structure provides afunction intended in the present invention.

FIGS. 8 and 9 illustrate a third embodiment of the present invention.

In the third embodiment, a case 3A includes projections 35A which areformed at different positions in comparison with those of the first andthe second embodiments. Specifically, in the third embodiment, each ofthe projections 35A has a base end which is connected to a correspondingfirst wall 32A below the longitudinally lower edge of a respective slit34. The case 3A includes second walls 32B each of which is formed withan opening 34 a connected to an upper portion of the corresponding slit34. The opening 34 a has a width Sa which is larger than the width Sb ofthe slit 34, as clearly shown in FIG. 8. As will be described later, bythe provision of the slit 34 a, the width Sc of the projection 35A ismade larger than the width Sb of the slit 34.

The case 3A is formed by using e.g. a mold 4A comprising an upper moldmember 42 and a lower mold member 43, as shown in FIG. 10. The uppermold member 42 includes a pair of projections 42 a each of whichincludes a portion 34′ corresponding to the slit 34 of the case 3A, aportion 34 a′ corresponding to the opening 34 a and a portion 30′corresponding to a portion of the receiving portion 30. Each of theprojections 42 a has surfaces 44 a, 44 b for defining an upper portionof a clearance 35A′ for forming the projection 35A. Other portions ofthe clearance 35A′ are defined by the lower mold member 43.

After the case 3A is molded by filling resin into the clearances 35A′and the other clearances of the mold 4A, the projections 42A of theupper mold member 42 can be lifted along the slits 34 without hindrance.Then, the case 3A can be readily removed from the lower mold member 43.Thus, also in the third embodiment, each of the slits 34 of the case 3Ais utilized as a slit for disposing and removing the upper mold member42 for forming the corresponding projection 35A. Therefore, in the case3A, large openings which extend vertically need not be provided inaddition to the slits 34. On the other hand, each of the openings 34 aof the second walls 32 b can be made smaller than an opening for forminga projection of a case in the prior art apparatus. As a result,disturbing external light is less likely to enter the receiving portions30 through the openings 34 a.

In this way, according to the present invention, each of the projectionsmay be formed in the case at a longitudinal edge of the correspondingslit as in the first and the second embodiments or at a portion awayfrom the slit as in the third embodiment. In the present invention, itis only necessary that the projection is connected to any portion of thecase on an extension line of the light transmission slit.

In the third embodiment described above, each of the projections 35A hasa width larger than that of the corresponding slit 34. Therefore, alsoin the case where the slit 34 is thin, the projection 35A can be madelarge to have a strength sufficient for preventing the LED lamp 1 andthe photodetector 2 from coming out. The ability of the photointerrupterin detecting an object increases as the width of each slit 34 decreases.Therefore, the structure of the case 3A in the third embodiment issuitable where each of the slits 34 needs to be narrowed to enhance thedetection ability. As is clear from the structure of the mold 4A shownin FIG. 10, the width Sc of each projection 35A may be equal to that ofthe corresponding opening 34 a at the maximum. In the present invention,the projection 35A may have a width equal to that of the slit 34. Inthat case, the width of the opening 34 a is made equal to that of theslit 34.

The specific structure of each of the components in the photointerrupterand the case in accordance with the present invention is not limited tothe embodiments described above, and may be modified in various ways.

For example, a light source other than the above-described LED lamp maybe employed. The photodetector may have a different structure from thatdescribed above. Further, the present invention may be applied for areflective type photointerrupter instead of a transmission typephotointerrupter. In the reflective type photointerrupter, light emittedfrom an LED lamp 1 is reflected at an object N and detected by aphotodetector 2, as shown in FIG. 11. The reflective typephotointerrupter is different from the transmission typephotointerrupter with respect to the orientation of a pair of slits 34formed in the case 3 and the arrangement of first walls 32A formed withthe slits 34. However, the basic structure may be similar to that of thetransmission type photointerrupter.

What is claimed is:
 1. A photointerrupter comprising a light source, aphotodetector, and a case, the case including a pair of receivingportions each of which is open at one end for receiving the light sourceor the photodetector, and a plurality of walls defining the pair ofreceiving portions; the plurality of walls of the case including a pairof first walls opposing each other and a pair of second walls eachextending transversely to a respective one of the first walls; eachfirst wall including a respective slit for light transmission and arespective projection which projects into a respective one of thereceiving portions for preventing the light source or the photodetectorfrom coming out of the respective receiving portion; each projectionbeing connected to the respective first wall on an extension line of therespective slit; each slit extending beyond the thickness of therespective first wall into the respective second wall by as much as therespective projection projects into the respective receiving portion. 2.The photointerrupter according to claim 1, wherein each projection isconnected to a longitudinal end edge of the respective slit.
 3. Thephotointerrupter according to claim 1, wherein the case is made of asynthetic resin, the pair of projections being integral with theplurality of walls.
 4. The photointerrupter according to claim 1,wherein each projection includes a base end connected to the respectivefirst wall and a tip end projecting into the respective receivingportion for engagement with one of the light source and thephotodetector.
 5. The photointerrupter according to claim 4, whereineach projection is elastically deformable for allowing movement of thetip end toward the respective first wall.
 6. The photointerrupteraccording to claim 4, wherein a rounded connection is provided betweenthe base end of each projection and the respective first wall.
 7. Thephotointerrupter according to claim 4, wherein each of the light sourceand the photodetector includes a bottom surface facing the opening ofthe respective receiving portion and a side surface facing therespective first wall; the tip end of each projection including a firstsurface and a second surface for engagement with the bottom surface andthe side surface, respectively.
 8. The photointerrupter according toclaim 1, wherein each of the slits has a first width in the respectivefirst wall and a second width in the respective second wall, the secondwidth being larger than the first width, each projection being connectedto the respective first wall at a portion away from a longitudinal endedge of the respective slit, the projection having a width larger thanthe first width.
 9. The photointerrupter according to claim 1, whereinthe light source comprises a light emitting element sealed in a resin,and a plurality of leads projecting from the resin in electricalconnection with the light emitting element.
 10. The photointerrupteraccording to claim 1, wherein the photodetector comprises a lightreceiving element sealed in a resin, and a plurality of leads projectingfrom the resin in electrical connection with the light receivingelement.
 11. A case for a photointerrupter comprising: a pair ofreceiving portions each of which is open at one end for inserting alight source or a photodetector; and a plurality of walls defining thepair of receiving portions; the plurality of walls including a pair offirst walls opposing each other and a pair of second walls eachextending transversely to a respective one of the first walls; eachfirst wall including a respective slit for light transmission and arespective projection which projects into a respective one of thereceiving portions for preventing the light source or the photodetectorfrom coming out of the respective receiving portion; each projectionbeing connected to the respective first wall on an extension line of therespective slit; each slit extending beyond the thickness of therespective first wall into the respective second wall by as much as therespective projection projects into the respective receiving portion.